Flame's Resolution
by Solera
Summary: Rin and Yukio were given a mission to give Spirit Wounds to a group of people. Tsuna and his Guardians are about to get their world turned upside down. Read more to find out.
1. Prologue

**Author's note**: Hi guys and gals! It's been a while since I posted another fanfic here at the site. Hopefully I won't be discontinuing this because of major plot twists happening within the two anime's I'm using for this crossover.

Thanks to Ao no Yoru and Hikou no Kokoro for the beta~

**Disclaimer:** I don't own KHR or Ao no Exorcist. It belongs to its respective owners.

**Original Release:** 09-11-11

**Edited Version:** 09-18-11

**IMPORTANT! READ THIS PLEASE:**

The timeline for Katekyo Hitman Reborn is right after Inheritance/Shimon/Daemon Spade Arc in the manga. The timeline for Ao no Exorcist (Blue Exorcist) is a week before the start of the canon. However, I'm going to change a few things with Blue Exorcist.

Rin has used his Flame before and had become an exorcist under Shiro (and Yukio). However, he's still a Page. Also, he doesn't have control over it like Episode 20 of the anime. I'm using the anime instead of the manga because I know that the stories are slightly different.

So without further ado, here's the story!

* * *

><p>Green eyes looked up at the sound of the door. "Rin-niisan, welcome home," the teen greeted his brother before returning to the book he was reading.<p>

"Ah. I'm home. Yukio, where's Tousan?" Rin asked after looking around for the old man.

Yukio took his attention off the book. "He was called for a mission," Yukio answered. "He won't be back for a few days."

"And he left me here with you," Rin grumbled.

"What was that Niisan?" Yukio inquired, craning his neck around to look at his brother directly. He set his book down, smirking as he waited a repetition of Rin's words.

"N-nothing! Nothing at all," Rin tittered.

Yukio sighed. "Niisan, you know why we can't bring you to missions yet."

Rin gumbled, "I know… I know."

Yukio looked at his brother with sympathy. _If only you didn't hold **his** flame._

* * *

><p>Tsuna sighed as another day passed by uneventfully. After so many things happened because of Daemon Spade's vengeance, the lull of activity made them uneasy. Tsuna was already expecting something to happen.<p>

Or rather, Reborn would plot and make them do _something_ again.

Reborn looked at his student. Perhaps it's time for his Spirit Wound… after all, Satan's son already awakened. If only Daemon Spade didn't launch the attack, Reborn would have done the initiation months ago.

Leon morphed into a phone and Reborn put it in his ear. "Ah. It's me," said Reborn when he heard a click. "I'll be expecting you then, Mephisto." Reborn closed the Leon-phone which promptly morphed back to his chameleon form.

Reborn looked at his student, then to Leon. "The next days would be fun. Wouldn't it, Leon?"

* * *

><p>Mephisto set down the phone and smirked. "So the Flame-keepers finally came," he said.<p>

"Who?" a teen with dark green hair asked. He has a spike of hair which is lightly colored compared to the rest. He wore a jacket that has cross bones as buttons. He also wears green arm warmers and a black and pink short sleeved shirt, which is of the same color as his spike, under his jacket which is ripped at the ends.

"You'll see, Amaimon. You'll see," Mephisto replied and picked up the phone again.

"_Yes? Okumura here," _a voice from the other side answered.

"Okumura-sensei, can you and your brother come to my office right now? Also, bring your equipment," requested Mephisto.

"_Niisan too…?"_ Yukio asked. "_Yes sir. We'll go there now."_

"Good, good. I'll be waiting." Mephisto ended the call and sat back, thinking of how he could use this opportunity.

* * *

><p><em>I wonder what Mephisto-san wants with Niisan and me…<em> Yukio thought as both of them prepared their stuff.

"Yukio, am I going to bring Kurikara?" Rin asked as he opened the cabinet holding said sword.

"Yes, Niisan," Yukio answered.

Rin took out the sword Kurikara and slid it in its red cloth container.

"Are you ready to go, Niisan?" Yukio asked. He was already in his exorcist attire.

Rin slipped the sword holster on his shoulder. "Yep. I'm ready."

Yukio took one of the keys given to him by Mephisto and inserted it through a locked door.

Mephisto grinned at the entrance of the Okumura twins. "Good afternoon to you both and welcome," he greeted and gestured for them to sit.

"Why did you call us here, Mephisto-san?" Yukio asked as he sat down.

"Business first as always neh, Okumura-sensei?" Mephisto said amused. "Well, I'm giving you two an interesting assignment."

Rin's ears perked up. "What kind of assignment Mephisto-san?" he asked excitedly.

"A friend of mine needs assistance in giving his charges Spirit Wounds," Mephisto grinned mischievously.

"So they would be budding exorcists then," Yukio said and nodded. "Where will we be going?"

"Namimori."


	2. Chapter 1

**Author's note**: Hi again!

Thanks for the reviews.

I re-uploaded Prologue chapter (last Sept 18, Sunday) because Hikou no Kokoro beta-ed it again. Hope you guys would re-read it.

**Original Release:** 09-27-11

Thanks to **Ao no Yoru **and **Hikou no Kokoro** for the beta~

* * *

><p><strong>Chapter 1<strong>

_Namimori?_ Yukio blinked. If he remembered right, Namimori was a place full of unexplained events. However, the Grigori never sent exorcists there for reasons unknown at the moment.

"You seem surprised, Okumura-sensei," Mephisto said.

"Ah. It's because of the order from the Vatican-" Yukio started but Mephisto cut him off.

"I received a letter of consent from the Vatican about this particular order," Mephisto interrupted as he took out the letter from a drawer. "My friend has _lots_ of friends and connections back in Italy. The Vatican is simply doing him a favor."

_What kind of friend does Mephisto have?_ The Okumura twins thought.

"Well, it's best if you go now," Mephisto handed two keys. "The silver one leads to any holy door in Nanimori. The gold one leads here at the True Cross Academy. Give this one to my friend."

Yukio accepted the keys and waited for further instructions.

"You may go." The twins stood and went for the door. "Ah. I forgot to warn you," Mephisto said. "No matter what abilities you see in my friend's charges. Remember that they are not demons."

Mephisto didn't explain more. They would know when they saw it.

* * *

><p>"Reborn, what are we doing here?" Tsuna asked as he, his Guardians, and Reborn stood in front of an old looking door.<p>

Reborn didn't say anything as he sat on Tsuna's head. Tsuna sighed, exasperated, at the expected silence. Or not-

"Turf-top get your hand off me!" Gokudera Hayato shouted.

Sasagawa Ryohei bristled and shouted back, "Who are you calling turf top, octopus head?"

"You are!" Hayato shouted back.

Lambo laughed at Hayato. "Octopus head!" he shouted again and again.

Hibari Kyouya became annoyed at the bickering guardians. "I will bite you to death for disturbing the peace," Kyouya said from his place at the door.

"Kufufufu. Feisty as ever, Skylark-kun," Rokudo Mukuro commented.

Then, the door opened.

"HIEE! What? How? Why?" Tsuna babbled out in surprise.

Reborn jumped down from his student and waited for their visitors.

Two teenagers came out of the door, one looking bothered and the other looking annoyed. "Niisan, would you please hurry up."

"I am hurrying, Yukio!"

Once the two of them got out, they turned to Tsuna's group.

"Greetings. I'm Okumura Yukio. An exorcist from the Order of True Cross," he said with a slight bow. Yukio wore a black overcoat over a white shirt and black pants. He had a utility belt holding two guns and several magazine rounds.

Yukio gestured to the one next to him. "This is my brother, Rin. He's a new recruit." Rin wore a white shirt and black pants. He also had a red cloth sword-holder slung on his back.

"Nice to meet you both," said Reborn. "I'm Reborn. Mephisto's friend.

Yukio and Reborn shook hands. "I assume these are your charges?" Yukio asked as they let go of each other's hand.

Reborn smirked. "Ah. They're under my supervision."

"Did Mephisto arrange you a place to stay at?" Reborn asked.

Yukio scratched his chin slightly. "As far as I remember, no… he hasn't."

"You can stay at Tsuna's or Yamamoto's house if you wish. There's no problem is there Yamamoto?" asked Reborn and faced Yamamoto Takeshi.

Takeshi just grinned in his usual self. "Of course there's no problem!"

"Then it's settled. Now for the introductions. The No-good brown haired is Sawada Tsunayoshi." Reborn said and introduced the other guardians including their rank in the Vongola Family.

"Reborn, why are they here?" Tsuna asked the question he was itching to ask earlier on. He dreaded the answer though. Because whatever Reborn did it was obviously to torture them again.

Reborn smirked, "They'll be your instructors for a while."

Tsuna groaned at how their life would be thrown into chaos again.

Yukio looked at the group of 7 teens (boy in case of Lambo) and a girl. "Would all of you interested in a strength test? I need to know what to work with."

Reborn agreed and grouped them. "Tsuna vs. Hibari. Gokudera vs. Ryohei. Yamamoto vs. Mukuro. Chrome and Lambo will stay out- for now." The guardians nodded. They regularly sparred with each other. Although usually, they had to goad Hibari with something.

"Ready," Reborn signaled.

Everyone lit up their rings with the Dying Will Flame and their Vongola gear came to life.

Tsuna had his X-Gloves Version Vongola Gear along with Natsu. Hibari had his Tonfa's out, engulfed in his Flame from the Bracelet of the Clouds Version X along with Roll. Gokudera had his dynamites from the Buckle of the Storm Version X and Uri. Ryohei had his boxing gloves and the Bangle of the Sun Version X and Kangaryuu. Yamamoto had his Shigure Kintoki out along with the Necklace of the Rain Version X and Kojirou out. Mukuro's Earring of the Mist Version X and Mukurowl were also showing alongside his Vongola Gear khakkhara.

Yukio and Rin were dumbfounded as they saw the rainbow of Flame. Now they understood Mephisto's warning _AND_ why the Vatican forbids this place from exorcists. An exorcist with a grudge on Satan would kill an innocent human because of the blue Flame one of the boys—Yamamoto Takeshi—held.

"Fight!"

The Okumura twins watched the fights with awe. Their level of fighting was incredible. Who are these people?

Reborn smirked at the twins' expressions and called off the spar. Hibari, Ryohei and Mukuro looked unsatisfied at the short sparring time.

"You seem surprised," Reborn said.

"We didn't expect that." Yukio coughed. "How do we go about what we came for? I can't see demons roaming around."

"That's true," Rin said in surprise. "I don't even see Coal Tars."

"Demons?" Tsuna asked, becoming scared.

Yukio looked at Tsuna before turning to Reborn. Seeing the question in his eyes, Reborn cocked an eyebrow. "They don't know of demons or Gehena. I believe only Mukuro does." Mukuro merely shrugged at the statement.

"How are we going to do this…" Yukio muttered to himself. "I was at least expecting Goblin lairs."

"Kufufufu," Mukuro laughed. "I'll lead you to a place that has demons. I believe I know what you've been sent for."

"Please do so then," Yukio said, relieved.

* * *

><p>Yukio started explaining the concept of Assiah and Gehena. "All Demons live in Gehenna. There are many different kinds of demons. The demons can pass over into the world of Assiah by possessing anything that exists within it."<p>

After Yukio finished his explanation, Mukuro stopped at a very familiar place. He had taken them to Kokuyo Land.

"I can certainly see why this place would harbor demons," Yukio commented at the sight of the ruined buildings.

"Kufufufu. You have no idea," Mukuro chuckled again.

"Yukio…" Rin murmured to him as he stared at the main building. "There's something there."

"Can you go ahead then, Niisan?" Yukio added, "You don't need to hold back."

"Eh? You serious?" Rin blurted out. "YOSH!" he said before running inside. Yukio chuckled.

"Your brother…. No. both of you are _his_ sons. Am I right?" Mukuro asked with a smirk.

Yukio just smiled at him sadly. "Indeed."

Tsuna looked at them confused. Whose son were they talking about?

* * *

><p><strong>AN:** Edited the chapter and changed Nanimori to Namimori. I still need my betas to edit the next chapter.


	3. Chapter 2

**Author's Note: ** Sorry for the delay for this chapter. I'll try to update faster next time. Thanks for all the reviews, favs and alerts!

I noticed I made Yukio a little OOC the last chapter and for this one… I'm sorry about that but I don't know how to change it D:

This chapter is not beta-ed

**Disclaimer: ** AoE and KHR don't belong to me.

**Chapter 2**

Rin followed the trail of what he guessed is a demon. Having sensed it from outside, Rin knew it would be powerful.

As he searched for the source, Rin thought of why Yukio didn't ban his Flames like the usual. _It must be because our clients have Flames, _Rin surmised. _They wouldn't find my Flames weird._

All of a sudden, pain shot through Rin's arm as he blocked an attack due to instinct. Rin grumbled to himself. Thinking while in enemy territory can kill you.

Looking around for the demon, Rin saw that he was dealing against a dog-like ghoul. He grinned to himself. _Nothing I can't handle._

Mukuro leaned near Yukio's ear which made the exorcist uncomfortable. "Everything with life has the Dying Will Flame. I happen to sense something… different from him."

Yukio was confused with what Mukuro said. "Dying will flame?"

Reborn jumped up to a waist-height wall nearby. "The Flames you saw earlier are the Dying Will Flames," Reborn explained. "There are seven typed. But we'll get to that some other time."

Reborn turned to Mukuro, "We'll talk later."

Mukuro nodded and smiled mischievously. "I'm rather surprised to see the Sky Flame in a demon. Let alone _his_ son."

Tsuna shrieked, "Demon?" but everyone ignored him.

Yukio stared at Mukuro with worry more than with confusion. Seeing this, Mukuro explained the power of his right eye. The Realm Of Hell* was connected to Gehena. However, it would not summon demons, but allow Mukuro to cast real illusions.

Reborn cut in before more could be said. He was interested in something more. "That's enough about Mukuro's eye. You said Rin Okumura's Flame was Sky?"

Rin was having trouble with the ghouls. He thought that there was only one. However, once he killed the first ghoul, two more came out of nowhere. Rin smacked himself mentally. He forgot his earlier assessment of the demon's power in the building.

Now, Rin was fighting five ghouls at once. A ghoul jumped towards Rin in an attempt to lash out its long claws. Rin blocked it with his sword, but the ghoul was proving to be slightly stronger. The other four ghouls attacked as one. Rin jumped after successfully pushing the first ghoul away due to the adrenaline pumping on his veins. However, the ghoul managed to scratch him in the process.

Rin could feel a burning sensation crawl up from his wounded leg travelling towards his upper body. He grit his teeth and willed his Flame to increase in order to deal with the problem.

Rin never noticed the difference of the Flame which answered his call.

Tsuna felt a strange feeling overcome him. It felt like the time when Dino showed them his Sky Flame. As well as the time when Byakuran, Uni, and Tsuna were together in the dome of Sky Flame. He didn't understand what it was, but he reckoned it to be a quirk of the Sky Flame users.

Tsuna jumped when Reborn's voice interrupted his thoughts. "What were you thinking about Dame-Tsuna?"

Tsuna squirmed slightly. "J-just a feeling. It's s-something to do with the Sky-"

Before he could finish his sentence, an explosion rang from the building Rin ran to. Tsuna immediately ran inside. Lambo, being on Tsuna's shoulder, and Reborn, who was at Tsuna's head, got dragged in. Yukio looked worried for his brother and also rushed inside. The others, except Hibari, Mukuro and Chrome followed the brunette.

Mukuro shrugged and walked leisurely with Chrome. Before getting too far, he glanced back at Hibari. "Skylark-kun~" Mukuro said in a singsong voice. "You better come inside as well."

Hibari glared at the pineapple-haired illusionist before going on the other direction. He didn't know Mukuro casted an illusion that made him go back inside every time he tried to go out of the place. Hibari growled when he noticed it.

He went inside the building that the other guardians went in. He swore to bite Mukuro to death for what he did.

Tsuna remembered this place as their first encounter with Mukuro and his gang. He looked around and saw some newer cracks and holes on the walls. That probably meant he was close to Rin and whatever he was fighting. Tsuna stopped to catch his breath from continuous running.

"Tenth!" Hayato cried out when he caught up with Tsuna. "Where are we going?"

Tsuna shook his head to tell him that he didn't know as well. "I… I just got this feeling that if we don't find Rin-san, something bad will happen."

Hayato nodded. "It's your hyper-intuition then, Tenth?" When his boss nodded, Hayato added: "Let's wait for the others. Baseball-freak(Yamamoto) or Mukuro can find him immediately with their box animals."

Soon enough, the other guardians and Yukio, minus the three that didn't join them in leaving, arrived at where Tsuna and Hayato waited. After explaining their problem about finding Rin, Takeshi brought out Jirou – his dog box animal – and asked him to seek out other Sky Flames. It was one of the abilities that Takeshi found out about Jirou. He could find any of the different Flames within an area.

Jirou sniffed around and ran off, leaving the guardians to follow him.

Yukio looked on in surprise as a dog materialized. It had blue flames adorning its whole body. It made him really curious about them, their abilities, and their connection to Satan's flames.

Rin coughed as miasma flooded the air. His body can't hold on for much longer. His vision became blurry. He could feel his body wavering. Rin didn't expect to be trapped by a demon that looked like a human.

He knew about demons possessing humans. Heck, Rin even awakened his demonic powers because of one! He just didn't expect to see one in here.

(Flashback)

"_Look out! Behind!" shouted someone._

_Rin quickly swung at his back and incinerated another ghoul. He looked around and saw a boy with brown hair and eyes clutching a large book. "Come near me! It's dangerous here!" the boy nodded and ran to Rin. "What's your name?"_

_The boy remained in silence. He watched Rin destroy the seemingly limitless amount of ghouls._

_Rin panted from using his flames too much and the damage dealt to him. "This is getting nowhere. I'm getting tired," Rin said and wiped his chin with the back of his left hand while his right still clutched Kurikara that was lit up with his flame._

_The boy laughed in a creepy manner. "I see. You still have no control over that flame."_

"_Huh?" Rin turned around in surprise._

_A huge mistake to make as miasma gas shot out from the boys' hands and engulfed him._

(End of flashback)

The boy laughed at how Rin struggled. "Master Astaroth will be happy. Even his Father would be if I bring you back to Gehena."

Rin glared at the best he could while his strength wavered more.

A dog covered with blue flames tackled the brown haired boy. Several people also came rushing after it. All of them froze at the sight of the boy. "Fuuta?" one of them asked in confusion.

Rin looked puzzled _They knew the boy?_ he thought. Rin coughed and remembered his current predicament with the miasma. His harsh cough seemed to wake the shocked guardians into action.

One of the white-haired teens went next to Rin immediately. He remembered the guy to be Sasagawa Ryohei. Ryohei took out his Sun Trowel and healed Rin. The others stood in front of them, ready to defend.

"Hey Tsuna," called out Takeshi without taking their eyes off the boy—Fuuta. "I thought he had Sky Flame? I can see Rain Flame on him though."

Tsuna, in Hyper Dying Will Mode, looked slightly at Rin before telling Takeshi: "Jirou found him by looking for Sky Flame."

"Ah you're right!" Takeshi grinned stupidly.

"Isn't Sky supposed to be the balance of all 6 Flames?" Ryohei asked in bewilderment.

Tsuna looked at Reborn who jumped down from his head beforehand. "Any clue, Reborn?"

"I'll tell you later," Reborn replied. "Deal with this first."

Yukio cocked his gun. "Please provide assistance to my brother while I deal with this."

"Very well," Reborn said.

Yukio took out a vial with Holy Water and threw its contents on the child. Fuuta screamed at the contact with the water.

"Damned exorcist!" the child snarled through the pain. "I'LL KILL YOU!"

Yukio smiled at him and pointed his gun. "Did you say something?"

"You wouldn't shoot a human!" the possessed boy said smugly.

"You want to bet on that?" Yukio said and lined his gun up for a shot.

The child laughed again, "You won't shoot!"

The sound of a gun being shot filled the air. The child held a surprised expression before closing his eyes. Yukio shot him in the shoulder.

"What did you do to Fuuta?" Tsuna glared at Yukio. Nobody hurts his Family.

"Calm down Dame-Tsuna," Reborn said from Fuuta's side. "He's only unconscious."

Yukio sheathed his gun. "I merely hit him with a tranquilizer. I don't kill humans." He walked over to Rin. "Are you alright Nii-san?"

"As alright as I can be," Rin grumbled while Ryohei still healed him.

"Uhm… Is Fuuta going to be fine?" Tsuna asked hesistantly. He left his dying will mode after Reborn calmed him.

"He'll be fine." Rin stood as Ryohei finished healing him. He stretched and sighed contently. "I feel as good as new. Thanks a lot Sasagawa-san!"

Ryohei shouted, "No problem to the extreme!"

Yukio and Rin looked thoughtful for a moment. Rin thumped a fist into his palm in a manner of blind inspiration. "Did you guys see the demon?"

Tsuna and his guardians questions, "The demon?"

"Guess not." Rin sighed in exasperation. "Then did you at least see my blue flames?"

"Yup!" Takeshi said while grinning. "This is the first time I saw a Sky bearer that had unbalanced Flames. Mukuro said that you had-"

"Kufufu." Mukuro materialized next to Rin who jumped in surprise. "I assure you my earlier assessment is correct."

"What the heck is this guy?" Rin blurted out.

Mukuro ignored Rin. "He does have a balanced Sky Flame."

Yukio coughed to get their attention. "I think we deserve an explanation about this Dying Will Flame you've been talking about."

Reborn looked up to him. "The Dying Will Flame is a high-density form of energy that is refined from one's own life-force. It also resonates with one's emotions. There are seven types of these."

Reborn gestured for the guardians to show their Flame. "Tsuna has the Sky Flame with the attribute of Harmony. Yamamoto has Rain which is Tranquility. Ryohei has Sun that is Activation. Mukuro has the Mist which is Construction. Lambo has Lightning having the attribute of Hardening. Gokudera has 5 types, but you already know the other 3. His main Flame, the red one, is Storm which would be Disintegration. The violet flame is Cloud which is propagation."

Yukio nodded in understanding. Rin still looked confused. "Does that mean I have Rain Flame?"

"No," Mukuro said with exasperation. "Your blue flames are not the same as the Dying Will. The have similarities, but they're not the same."

"Oh. I see," said Rin, even though he didn't understand. "Then what do I have?"

"Sky."

**A/N:** Sorry for the delay. I was waiting for responses from my two betas. For Rin's Flame, I'll explain that on the next chapter.


End file.
